Theory predicts that a charge added to a conjugated polymer chain forms a polaron Recent calculations of the three-dimensional band structure of trans-polyacetylene, t-PA, and poly(phenylene vinylene), PPV, have obtained values for the interchain coupling that are large enough to destabilize the polaron. Nevertheless, there is experimental evidence that polarons exist in these materials. We show that the existence of chain endings and other conjugation breaks can stabilize the polaron in actual samples.